The present invention pertains to a device for sealing between the guide vanes and the rotor of turbomachines, especially gas turbines.
In a seal in turbomachines, which has been known from practice, the inner ring suspended on the guide vanes with the soldered honeycomb seal is uncooled. To reliably avoid a metallic contact between the rotor and the stator of the turbomachine, the distance between the honeycomb seal and the tips of the labyrinth must be dimensioned to the largest possible amount of the thermal expansion. The relatively great distance leads to a large leakage flow.
A cooled honeycomb seal, which is arranged at the outer limitation of the flow channel within a gas turbine, has been known from DE-A 19 821 365. Part of the cooling air, which is available to the guide vane located upstream at the outer shrouding, is fed for cooling to the honeycomb seal through holes in the ring carrying the honeycomb seal.
Gas turbines with internally cooled guide vanes have been known from U.S. Pat. Nos. 5,749,701 and 5,157,914. Sealing segments, which contain a honeycomb seal, are rigidly connected to the guide vanes. The sealing segments are fixed radially and are not suspended in a thermally elastic manner. Cooling air is fed to the sealing segments from the cooled guide vanes. This cooling air is used above all to block the sealing gap between the sealing segments and labyrinth tips and less to cool the honeycomb seal. The width of the sealing gap is not affected by the cooling air because of the non-thermally elastic suspension of the sealing segments.
The basic object of the present invention is to design the seal of this type such that the distance between the honeycomb seal and the labyrinth tips can be reduced to reduce the leakage flows while increasing the efficiency of the turbomachine at the same time.
According to the present invention a device for sealing between the guide vanes and the rotor of turbomachines, especially gas turbines with an inner ring suspended on the vane footing of the guide vanes in a thermally elastic manner with a soldered honeycomb seal and labyrinth tips arranged on the rotor. Each guide vane has a cavity through which cooling air flows. First flow channels are connected to the cavities of the guide vanes. The first flow channels are led through the vane footings of the guide vanes and the flow channels are connected to at least one of second flow channels. The second flow channels are led to the vicinity of the honeycomb seal and to which at least one connection leading to the outside of the inner ring is connected.
The second flow channels may open into at least one of axial third flow channel, which are open at the rear edge of the inner ring and form connections of the second flow channels, which connections lead to the outside of the inner ring. The second flow channels may be led to an annular groove open toward the honeycomb seal on the underside of the inner ring, which forms the connection of the second flow channels, which connection leads to the outside of the inner ring.
Fourth flow channels, which may be led to another annular groove open toward the honeycomb seal on the underside of the inner ring, may be branched off from the second flow channels.
The first flow channels may be designed as a hole each passing through the vane footing of the guide vanes. The first flow channels may be designed as an inner hole led through a hollow centering pin and as a hole connecting the inner hole to the cavity of the guide vane.
The second flow channels may be designed as holes led radially through the inner ring or as holes led three-dimensionally diagonally. The third flow channels may be designed as holes led axially through the inner ring. The fourth flow channels may be designed as holes led obliquely through the inner ring.
The inner ring may comprise two parts, which are provided with grooves and projections on sides facing each other. The grooves and projections may engage one another such that a serpentine-like, fifth flow channel is formed, to which at least one connection leading to the outside of the inner ring is connected.
The honeycomb seal may be protected by the cooling air discharged from the honeycomb seal and/or the inner ring against the break-in of hot gas.
The amount of the cooling air fed to the inner ring can be regulated and depending on the amount of the cooling air, the leakage flows flowing through the gap between the honeycomb seal and the labyrinth tips can flow only forward or both forward and backward. The amount of the cooling air fed to the inner ring can be regulated by the pressure of the cooling air in the guide vane, the diameter of the holes or by selecting the shape of the inlet and outlet of the holes.
The annular gap between the honeycomb seal and the labyrinth tips, which gap acts as a sealing gap, is determined decisively by the temperature of the inner ring suspended in a thermally elastic manner. The cooling air led through the inner ring cools this ring and thus lowers its component temperature. As a result, a smaller internal diameter of the honeycomb seal and consequently also a smaller annular gap become established because of the lower thermal expansion. Due to the inner ring being supplied with cooling air, the width of the sealing gap can thus be affected. The sealing gap can be dimensioned to be narrower from the very beginning.
Furthermore, the break-in of hot gas from the flow channel of the guide vanes into the honeycomb seal is avoided and the leakage flow will also decrease correspondingly as a result. This is associated with an increase in the efficiency of the turbomachine. The life-limiting material temperature is reduced, the temperature resistance and the corrosion resistance of the components affected are improved, and the service life of the part of the turbomachine exposed to hot gas is prolonged due to the cooling of the inner ring and of the honeycomb seal. A metallic contact between the rotor and the stator in transient states of the turbomachine can be avoided by regulating the cooling. Because of the advantageous properties indicated, the present invention is especially suitable for the hub sealing between the rotor and the stator of gas turbines.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.